1. Field of the Invention
The present invention relates to a method and apparatus for adhering a friction material to a core plate of a lockup clutch that is used for an automatic transmission of a vehicle or the like.
2. Related Background Art
FIGS. 4, 5A and 5B show a conventional method and apparatus for adhering a friction material to a core plate of a lockup clutch. An adhering apparatus 101 has a jig 102 for positioning a core plate 120 and a friction material 121 that has been formed into an annular shape by blanking and a pressing jig 103 that is so disposed as to be opposed to the jig 102. The pressing jig 103 is adapted to be lowered from above to press the core plate 120 and the friction material 121. The jig 102 and the pressing jig 103 are maintained to high temperatures by heaters 105 and 106 respectively.
The friction material 121 is applied with adhesive made of a thermosetting resin that has been dried and cured. When the core plate 120 and the friction material 121 are heated and pressed by the adhering apparatus 101, the adhesive is once softened and then cured completely to attain adhesion.
However, the above-described adhering method and apparatus suffers from a problem as follows. The core plate is formed into a prescribed shape by blanking and drawing, and, in some cases, it is further processed by heat. However, a slight deformation sometimes remains in the core plate after those formation processes. In order to eliminate the deformation, cutting is performed on the side surface of the core plate to which a friction material is to be adhered, so that required precision in size is attained. On the other hand, it is economically preferable to omit cutting of the side surface opposite to the side surface to which the friction material is adhered, since such precision in size is not required for the opposite side surface from the viewpoint of the product performance.
However, if the adhering is performed on the core plate having such a residual deformation by the above described method and apparatus, as shown in FIG. 5A, the deformation on the opposite surface 123 of the core plate 120 affects the adhesion surface 122, as the core plate is pressed by the pressing jig 103. In spite that under the pressed state, the deformation is absorbed by elastic deformation of the friction material 121, after the completion of the adhesion, a deformation will occur in the friction material. This deformation will cause a judder, when the lockup clutch is caused to slip in an automatic transmission.